In the past few years, mobile homes have become a significant part of the residence inventory in the United States. Mobile homes, which were once considered suitable only for temporary and barely adequate residential use, have now become permanent residences for large segments of the population. This has been due to a number of factors, not the least of which are the improvements in mobile home construction, design and furnishing and the cost of conventional dwelling. The transition of mobile home parks into the equivalent of tradition neighborhoods and communities has also been an important factor.
The mobile home frame is built of longitudinal beams such as I-beams or C-beams supporting the mobile home floor and the rest of the mobile home structure. In conventional practice a number of small concrete pads are poured in place or otherwise positioned on the ground in the location where the mobile home is to be placed. On each of these pads is placed a support, with the supports and pads being aligned with the longitudinal beams of the mobile home. The mobile home is then placed on the supports so that the beams rest on the top of the supports and the supports in turn rest on the pads. The supports can be made of different heights to allow the mobile home to be level even though the ground beneath the mobile home may have slight irregularities. Commonly the supports, which are generally similar to an automobile jack stand, are on the order of 1 to 2 feet (0.3 to 0.6) in height. The number of supports under a mobile home will be determined by the size and weight of the mobile home as well as the number of longitudinal beams in the mobile home frame.
In many areas of the country where there are large concentrations of mobile homes, there is also a history of past and current earthquake activity, the most notable such area being California. Small tremors are quite common and more severe shocks (up to about 6.0 on the Richter Scale) are not uncommon, as is evidenced by the Palm Springs earthquake of 1986 and the Whittier earthquake of 1987. Most such earthquake are accompanied by large numbers of foreshocks and aftershocks of varying intensity.
It has been found that in such earthquakes, among the most severely damaged structures are mobile homes. It is common for a much larger proportion of mobile homes in a quake area to be damaged severely than the corresponding proportion of conventional foundation homes. Primarily this is due to the inability of the conventional mobile home supports to support the mobile home adequately during the tremor. The support failure normally occurs in either of two ways: collapse of the supports themselves which allows the mobile home to fall, or vibration which causes the mobile home to move laterally off of the supports and fall.
Past efforts to provide earthquake resistance to mobile home support have involved the design of complex structures which are intended to provide support to several parts of the structure in several directions. Typical are those supports shown in U.S. Pat. Nos. 4,562,673; 4,546,581; 4,522,000; 4,417,426; 4,373,307; 4,348,843 and 4,261,149. These have been generally unsatisfactory because they are still susceptible to bending or buckling, they do not necessarily compensate for lateral motion of the mobile home and they are complex and costly to fabricate and install. In addition, the conventional supports are prone to rust, particularly in the humid environment found under most mobile homes, especially those surrounded by skirting. The rusted metal supports lose most of their strength and easily fracture when subjected to the forces of an earth tremor. Because of these shortcomings, the prior art structures usually cannot be approved by responsible earthquake safety authorities, such as the Department of Housing and Community Development in the State of California.
It would therefore be most advantageous if there were a mobile home support of relatively simple structure which could provide effective support during common earth tremors, to minimize or eliminate damage to mobile homes from the tremors, and which would be simple and economical to construct and install. It would also be of real importance for the support to be sufficiently effective that it would qualify for approval from recognized earthquake safety authorities.